Objective

Objective Questions and Answers

Refraction of light

Question-1. When light enters from one transparent medium to another transparent medium, it bends towards the normal or away from the normal. This event is called

Ans- Refraction of light

Question-2. How many laws of refraction of light are there?

Ans- Two

Question-3.The ratio of the sine of the angle of incidence and the sine of the angle of refraction is a constant for any two mediums and for a given color (color) of light. What is this rule called?

Ans- snell's law

Question-4. When a ray of light incident at non-zero angle of incidence passes from a rarer medium to a denser medium, where does it bend?

Ans- towards the normal

Question-5. When a ray of light incident at a non-zero angle of incidence passes from a denser medium to a rarer medium, where does it depart?

Ans- far from normal

Question-6. Light travels through different mediums.

Ans- different (different)

Question-7. Light travels in a vacuum.

Ans- 3 x 10⁸ m/s

Question-8. The ratio (refractive index) of the speed of light (c) in a vacuum and the speed (v) of light in that medium is

Ans- c/v

Question-9. The medium whose refractive index is low, the speed of light is there.

Ans- More

Question-10. What is the ratio of the absolute refractive indices of two media called?

Ans- relative refractive index

Question-11. The angle of incidence of a denser medium for which the angle of refraction becomes 90⁰ is called

Ans- critical angle

Question-12. If the angle of incidence in the denser medium is greater than the critical angle, then all the incident rays return to the denser medium, then what is it called?

Ans- total internal reflection of light

Question-13. What is the perpendicular distance between the incident ray and the emerging ray called?

Ans- lateral displacement

Question-14. When a transparent material is a block surrounded by two surfaces, what is it called?

Ans- Lens

Question-15. What is it called when the curved surface of the lens is spherical?

Ans- spherical lens

Question-16. How many types of spherical lenses are there?

Ans- Two (convex lens and concave lens)

Question-17. Which lens is called a concave lens?

Ans- diverging lens

Question-18. Which lens is called a convex lens?

Ans- converging lens

Question-19. A lens that is thin at the edges and thick in the middle is called which lens?

Ans- convex lens

Question-20. A lens that is thick at the edges and thin in the middle is called which lens?

Ans- concave lens

Question-21. The center of a convex lens and a concave lens is called.

Ans- center of curvature

Question-22. The straight line joining the centers of curvature (C₁ and C₂) of the surfaces of a lens is called a lens.

Ans- main-axis

Question-23. The point at which the light-rays parallel and near the principal axis of the lens converge on the principal axis after refraction is called.

Ans- main focus

Question-24. How many focuses does the lens have?

Ans- Two

Question-25. What is the distance between the optical center of the lens and the principal focus called?

Ans- Focus Distance (Focus Alternate)

Question-26. The image of an object is formed by a concave lens.

Ans- imaginary (virtual) and direct

Question-27. Image of an object is formed by a convex lens.

Ans- both real and virtual

Question-28. The size and nature of the image of an object formed by a convex lens or a concave lens depend on it.

Ans- the distance of the object from the lens

Question-29. What is lens formula?

Ans- 1/v - 1/u = 1/f

Question-30. What is the ratio of the height (size) of the image to the height (size) of the object called?

Ans- Magnification (m)

Question-31. What is the formula for the magnification (m) produced by a lens?

Ans- m= h'/h = v/u

Question-32. What is the power of a lens called?

Ans- lens capacity

Question-33. What is the SI unit of lens power?

Ans- Diopter (D)

Question-35. The second focus-distance of a convex lens according to the coordinate sign convention is?

Ans- positive

Question-36. The second focus-distance of a concave lens according to the coordinate sign convention is?

Ans- negative

Question-37. Convex lens has the power—

Ans- positive

Question-38. The power of a concave lens is—

Ans- negative

Question-39. What happens between thin lenses?

Ans- optical center

Question-40. The power of the lens is expressed.

Ans- by inverse of focus-distance

Question-41. What is the maximum speed of light?

Ans- in vacuum (zero)

Question-42. Which of the following materials is not used to make lenses?

(a) Glass (b) Clay (c) Water (d) Plastic

Ans- (b) soil

Question-45. If the focal length of a convex lens is 20 cm, what will be the power of the lens?

Ans- +5 D (Diopter)

Question-46. The power of a lens is -2.0 D (diopters), then which lens will it be?

Ans- concave lens

Question-47. Where will the object be placed in front of a convex lens to obtain a real and uniform sized image of an object?

Ans- at twice the focus-distance

Question-48. If the object is placed between the focus of a convex lens and twice the focal length, what will be the image obtained?

Ans- real, inverted and magnified

Question-49. Which lens would you prefer while reading the given small letters in a dictionary?

Ans- 5 cm focus-distance convex lens

Question-50. What is the effective diameter of the circular contour of a spherical lens called?

Ans- Dwarak

Question-51. What is the refractive index of a transparent medium?

Ans- sin i / sin r

Question-52. There is Snell's law.

Ans- sin i / sin r = constant

Question-53. Thin lenses have magnifying power.

Ans- Less

Question-54. Thick lenses have magnifying power.

Ans- more

Question-55. A lens which has a raised mid-plane is called which lens?

Ans- convex lens

Question-56. The lens whose mid-plane is sunken (inwards) is called which lens?

Ans- concave lens

Question-57. What type of lens are eyes?

Ans- convex lens

Question-58. What produces a ray of light passing through a rectangular glass slab placed in a transparent medium?

Ans- lateral displacement

Question-59. If a concave lens and a convex lens of equal focal length are placed in contact, how will the combined lens work?

Ans- like a glass block

Question-60. What is the nature of image of an object placed between the optical center and principal focus of a convex lens?

Ans- imaginary (virtual) and upright

Question-61. Place the image at the principal focus of a convex lens.

Ans- at infinity

Question-62. The position of the image of the object placed at the principal focus of a concave lens is

Ans- between optical center and focus

Question-63. The position of the image of an object placed at infinity in front of a concave lens is

Ans- on focus

Question-64. If the magnification produced by a lens (m) = -1, what will be the position of the object?

Ans- at the center of curvature of a convex lens

Question-65. The focal length of a lens with 2 D (diopter) power is—

Ans- 40 cm

Question-66. Which lens produces both real and virtual images?

Ans- in a convex lens

Question-67. If the power of a lens is +5 D (diopters), what type of lens will it be?

Ans- convex lens

Question-68. Where should the position of the object be for a convex lens to form a virtual and magnified image of the object?

Ans- between lens and focus

Question-69. Where will the image be formed when the object is placed in front of a convex lens?

Ans- at the center of curvature

Question-70. What is the refractive index of water?

Ans- 1.33

Question-71. What is the refractive index of diamond?

Ans- 2.42

Question-72. How many focus does the lens have?

Ans- Two (F and F₂)

Question-73. In which lens only imaginary image is formed?

Ans- concave lens

Question-74. If the magnification of the image of an object is negative, then what will be the nature of that image?

Ans- real and reverse

Question-75. Which lens has positive focus-distance?

Ans- of convex lens

Question-76. Which lens has negative focus-distance?

Ans- of concave lens

Question-77. In which medium the speed of light is maximum?

(a) air (b) water (c) lead (d) diamond

Ans- (a) हवा